A New Source Of Power Rises Over Ground Zero

By DAVID W. DUNLAP

Published: May 25, 2004

Early on Sunday, May 16, with no fanfare, power began flowing through the Con Ed substation at the World Trade Center for the first time since 4:33 p.m. on Sept. 11, 2001.

Tomorrow, Gov. George E. Pataki, speaking by phone from the substation to Con Ed's energy control center uptown, will make it official: one more vital piece of the infrastructure around the trade center site is back in place, following the restoration of the subway tunnel for the Nos. 1 and 9 lines in 2002 and the opening of the temporary PATH station last year.

''In my 41 years with the company, this is the most difficult and complicated substation project I've ever built,'' said Eugene R. McGrath, chairman and chief executive of Consolidated Edison. The final project budget has yet to be tallied, but company officials said that constructing a new substation in Manhattan might be expected to cost about $100 million.

The new substation, like the structure it replaces, doubles as the base of Silverstein Properties' 7 World Trade Center office building, across Vesey Street from the main trade center site. About 20 floors of steel now rise above the substation's 80-foot tall concrete shell.

Three transformers in the substation will each put out 80 megawatts of power. (The trade center used about 110 megawatts.) The substation now serves Battery Park City but will also eventually power the rebuilt trade center.

As many as seven transformers can be added. ''This new substation will not only fully replace what we lost on Sept. 11,'' Mr. Pataki said in a statement, ''but will also be large enough to accommodate the new electric demand that is expected.''

In theory, only one transformer is needed today. But Stephen E. Quinn, the vice president for substation operations, said Con Ed builds in a double contingency, under which one of the transformers could be shut down for maintenance, another transformer could fail and the substation could still send out the needed power with the remaining transformer.

On the afternoon of the attack, Con Ed officials shut down the nine-transformer substation shortly before 7 World Trade Center collapsed. No one was killed or injured at the substation, but a retired Con Ed vice president for emergency management, Richard Morgan, died at the twin towers, where he had rushed that morning to offer assistance.

Con Ed managed to cope after the attack by adding five transformers to a nearby substation. The destruction of the trade center also substantially reduced demand.

The new substation is shaped to permit the opening of a private driveway along what was once Greenwich Street, a route blocked by the old 7 World Trade Center. The new form required squeezing the 40-foot-high transformer vaults tightly and stacking the switch gear overhead, no easy feat with cables so thick they need a five-foot turning radius.

This engineering challenge came on top of the already daunting task of restoring the underground power grid while Verizon, a next-door neighbor at 140 West Street, was trying to restore the intertwined ganglia of the telecommunications grid and the city was rebuilding sewer and water lines. ''It's truly a story below ground,'' Mr. Quinn said.

Area substations play the critical role of reducing the very high-voltage power from generating stations into a more manageable current that can be distributed across a small local network to residential and commercial customers.

At the trade center substation, power arrives through 138,000-volt cables. The cables run up to ceramic devices known as potheads, above which aluminum strands carry the power through circuit switchers and down to movable arms. When those arms swing into position, the electricity completes its journey to the transformers, from which it emerges at 13,000 volts. It then runs through the switch gear upstairs -- in essence, automated circuit breakers -- before it is sent out again under the streets to customers.

The $1.1 million transformers were made in Austria by Va Tech. Each is 20 feet tall, weighs 168 tons and is cooled by a giant radiator. It is the radiators -- not the transformers -- that are visible from the street, with their vertical cooling fins topped by large tanks holding mineral oil-based coolant.

Con Ed has 23 other substations in Manhattan. The company does not identify them, but they are not hard to spot if you have one in your neighborhood: a low, windowless, nameless building, often with colossal external vents to cool the transformers inside, surrounded by chain-link fences and, sometimes, concrete barriers.

By contrast, the trade center substation will be turned into a work of environmental art by James Carpenter Design Associates, working with the architectural firm of Skidmore, Owings & Merrill. It will be clad in ranks of prismatic stainless-steel bars, arranged in alternating angles to reflect different sections of the sky and surrounding streetscape. There will be a cavity behind the bars inside of which light-emitting diodes will be installed that can create changing patterns.

''The whole desire was to activate the base of the building,'' said Mr. Carpenter, who is also the collaborating artist on the Fulton Street Transit Center project, the design of which is to be unveiled tomorrow.

Photo: The Con Ed plant will double as the base of 7 World Trade Center. (Photo by Fred Conrad/The New York Times)